Dopamine is the brain’s motivational spark, driving us to chase what feels good and steer clear of what doesn’t. But scientists haven’t fully understood how dopamine helps us learn to avoid bad outcomes. A study in mice carried out by researchers at Northwestern University has now found that dopamine signals in two key brain areas involved in motivation and learning respond differently to negative experiences, helping the brain to adapt based on whether a situation is predictable or controllable.
The findings showed that dopamine signals in the two parts of the brain rise and fall in complex patterns as the animals learned to avoid danger. While previous research has shown that dopamine can respond to negative experiences, this is the first study to track how those signals evolve over time as animals progress from being a novice to an expert in avoiding them.
The study authors said their results may help explain how we learn from bad experiences and why some people learn to avoid danger better than others. They also shed light on how excessive avoidance—a hallmark symptom of multiple psychiatric conditions such as anxiety, obsessive-compulsive disorder (OCD), and depression—may come to be via alterations in dopamine function. This can lead to an overestimation of danger in the environment and a decreased quality of life as the brain prioritizes avoiding certain experiences.
The study, in addition, helps explain why the concept behind the recent “dopamine-detox” wellness trend is too simplistic. “Dopamine is not all good or all bad,” said Gabriela Lopez, a doctoral candidate in the Interdepartmental Neuroscience Program at Northwestern University Feinberg School of Medicine. “It rewards us for good things but also helps us tune into cues that signal trouble, learn from consequences, and continuously adapt our learning strategies in unstable environments.”
First author Lopez and colleagues reported on their findings in Current Biology, in a paper titled, “Region-specific nucleus accumbens dopamine signals encode distinct aspects of avoidance learning.”
Avoidance learning—learning to avoid bad outcomes—is an important survival behavior, the authors wrote. “It is essential for survival but can become maladaptive when performed in excess, as in anxiety disorders, obsessive-compulsive disorder (OCD), and depression.” And while dopamine has been well studied in the context of positive reinforcement, i.e., the receipt of something good, dopamine neurons also respond to aversive stimuli and associated cues, they continued. “Dopamine signals are widely observed in response to aversive stimuli, indicating they could play a role in learning about how to avoid these stimuli … Available evidence supports a role for dopamine in avoidance learning, but the region specificity and evolution of dopamine responses during learning remain in question.”
For their reported study, the scientists trained mice to respond to a five-second warning cue that predicted an unpleasant outcome. If the mice moved to the other side of a two-chamber box during the warning cue, they could avoid the outcome entirely. As the mice learned the task (the animals completed 30 trials daily for seven days), the researchers recorded dopamine activity in two areas of the nucleus accumbens (NAc), a brain region involved in motivation and learning. Previous research had suggested that dopamine in the ventromedial shell of the nucleus accumbens (vmShell) increases during bad experiences, while dopamine in the core of the nucleus accumbens (Core) decreases. The scientists wanted to understand how these different dopamine responses work together when the mice learn to avoid bad experiences.
The results of their tests with the mice indicated that the two areas of the nucleus accumbens responded differently as the animals learned to avoid the unpleasant experience. The team found that in the ventromedial shell, dopamine levels initially surged in response to the unpleasant event itself. As the mice actively learned about the meaning of the warning cue, the dopamine response shifted to the cue itself. Eventually, though, the dopamine response faded away as the mice became skilled at avoiding the outcome. In the core, dopamine decreased for both the unpleasant event and the warning cue. The reduction in dopamine in response to the warning cue steadily increased throughout training, especially as the mice became more successful at avoiding the event.
Summarizing their findings, the researchers wrote, “We found that NAc Core and vmShell dopamine signals display different dynamics across learning during an active avoidance (negative reinforcement) task. Both signals evolved substantially—but differently—with learning. We found that Core and vmShell dopamine signals responded oppositely to shocks at the beginning of training and oppositely to warning cues as cue-shock associations developed in mid-training. Core dopamine responses strengthen with learning and are especially evident during expert performance. vmShell dopamine responses to cues and shocks were present during early learning but were not sustained during expert performance.”
Corresponding author Talia Lerner, PhD, associate professor of neuroscience and psychiatry and behavioral sciences at Feinberg, commented, “These responses are not only different in their sign—where in one area, dopamine goes up for something bad and, in the other area, it goes down for something bad—but we also saw that one is important for early learning while the other one is important for later-stage learning.” The authors further noted, “Our data illustrate how Core and vmShell dopamine signals vary by subregion and how their computations relate to learned behavioral strategies as mice transition from naive to expert avoidance … Our data support a model in which Core dopamine encodes prediction errors that guide the consolidation of avoidance learning, while vmShell dopamine guides initial cue-shock associations by signaling aversive salience.”
The researchers, in addition, tested what would happen when the outcome couldn’t be avoided, regardless of how the mice acted. Under those conditions, dopamine patterns returned to what they looked like earlier in training, suggesting that these brain signals are sensitive to context and may help animals adapt their behavior when the environment changes. “This shows that the dopamine signals are flexible, sensitive to task rules, and may help us adapt to changes in the environment,” Lopez said.
There has been interest in the “dopamine detox” wellness trend, which involves cutting out things that trigger a dopamine rush, such as eating junk food or scrolling social media, to regain control over these behaviors. The newly reported study may help to explain why the concept of a “dopamine detox” is too simplistic. “We think of dopamine as a learning molecule that is important for normal behavior in everyday life,” Lopez said. “So, cutting it out completely can do more harm than good … The dopamine signals we are studying are important for representing aversive signals that are involved in problems like chronic pain, depression, and withdrawal from addictive substances.”
Overactive avoidance learning may also be a pathway that contributes to obsessive-compulsive disorder and other clinical anxiety disorders, suggested Lopez. “We hope to follow up on these basic research findings to address clinical problems affecting patients.”
The post Region Specific Shifts in Dopamine Signaling Plays Role in Learning to Avoid Danger appeared first on GEN - Genetic Engineering and Biotechnology News.
The findings showed that dopamine signals in the two parts of the brain rise and fall in complex patterns as the animals learned to avoid danger. While previous research has shown that dopamine can respond to negative experiences, this is the first study to track how those signals evolve over time as animals progress from being a novice to an expert in avoiding them.
The study authors said their results may help explain how we learn from bad experiences and why some people learn to avoid danger better than others. They also shed light on how excessive avoidance—a hallmark symptom of multiple psychiatric conditions such as anxiety, obsessive-compulsive disorder (OCD), and depression—may come to be via alterations in dopamine function. This can lead to an overestimation of danger in the environment and a decreased quality of life as the brain prioritizes avoiding certain experiences.
The study, in addition, helps explain why the concept behind the recent “dopamine-detox” wellness trend is too simplistic. “Dopamine is not all good or all bad,” said Gabriela Lopez, a doctoral candidate in the Interdepartmental Neuroscience Program at Northwestern University Feinberg School of Medicine. “It rewards us for good things but also helps us tune into cues that signal trouble, learn from consequences, and continuously adapt our learning strategies in unstable environments.”
First author Lopez and colleagues reported on their findings in Current Biology, in a paper titled, “Region-specific nucleus accumbens dopamine signals encode distinct aspects of avoidance learning.”
Avoidance learning—learning to avoid bad outcomes—is an important survival behavior, the authors wrote. “It is essential for survival but can become maladaptive when performed in excess, as in anxiety disorders, obsessive-compulsive disorder (OCD), and depression.” And while dopamine has been well studied in the context of positive reinforcement, i.e., the receipt of something good, dopamine neurons also respond to aversive stimuli and associated cues, they continued. “Dopamine signals are widely observed in response to aversive stimuli, indicating they could play a role in learning about how to avoid these stimuli … Available evidence supports a role for dopamine in avoidance learning, but the region specificity and evolution of dopamine responses during learning remain in question.”
For their reported study, the scientists trained mice to respond to a five-second warning cue that predicted an unpleasant outcome. If the mice moved to the other side of a two-chamber box during the warning cue, they could avoid the outcome entirely. As the mice learned the task (the animals completed 30 trials daily for seven days), the researchers recorded dopamine activity in two areas of the nucleus accumbens (NAc), a brain region involved in motivation and learning. Previous research had suggested that dopamine in the ventromedial shell of the nucleus accumbens (vmShell) increases during bad experiences, while dopamine in the core of the nucleus accumbens (Core) decreases. The scientists wanted to understand how these different dopamine responses work together when the mice learn to avoid bad experiences.
The results of their tests with the mice indicated that the two areas of the nucleus accumbens responded differently as the animals learned to avoid the unpleasant experience. The team found that in the ventromedial shell, dopamine levels initially surged in response to the unpleasant event itself. As the mice actively learned about the meaning of the warning cue, the dopamine response shifted to the cue itself. Eventually, though, the dopamine response faded away as the mice became skilled at avoiding the outcome. In the core, dopamine decreased for both the unpleasant event and the warning cue. The reduction in dopamine in response to the warning cue steadily increased throughout training, especially as the mice became more successful at avoiding the event.
Summarizing their findings, the researchers wrote, “We found that NAc Core and vmShell dopamine signals display different dynamics across learning during an active avoidance (negative reinforcement) task. Both signals evolved substantially—but differently—with learning. We found that Core and vmShell dopamine signals responded oppositely to shocks at the beginning of training and oppositely to warning cues as cue-shock associations developed in mid-training. Core dopamine responses strengthen with learning and are especially evident during expert performance. vmShell dopamine responses to cues and shocks were present during early learning but were not sustained during expert performance.”
Corresponding author Talia Lerner, PhD, associate professor of neuroscience and psychiatry and behavioral sciences at Feinberg, commented, “These responses are not only different in their sign—where in one area, dopamine goes up for something bad and, in the other area, it goes down for something bad—but we also saw that one is important for early learning while the other one is important for later-stage learning.” The authors further noted, “Our data illustrate how Core and vmShell dopamine signals vary by subregion and how their computations relate to learned behavioral strategies as mice transition from naive to expert avoidance … Our data support a model in which Core dopamine encodes prediction errors that guide the consolidation of avoidance learning, while vmShell dopamine guides initial cue-shock associations by signaling aversive salience.”
The researchers, in addition, tested what would happen when the outcome couldn’t be avoided, regardless of how the mice acted. Under those conditions, dopamine patterns returned to what they looked like earlier in training, suggesting that these brain signals are sensitive to context and may help animals adapt their behavior when the environment changes. “This shows that the dopamine signals are flexible, sensitive to task rules, and may help us adapt to changes in the environment,” Lopez said.
There has been interest in the “dopamine detox” wellness trend, which involves cutting out things that trigger a dopamine rush, such as eating junk food or scrolling social media, to regain control over these behaviors. The newly reported study may help to explain why the concept of a “dopamine detox” is too simplistic. “We think of dopamine as a learning molecule that is important for normal behavior in everyday life,” Lopez said. “So, cutting it out completely can do more harm than good … The dopamine signals we are studying are important for representing aversive signals that are involved in problems like chronic pain, depression, and withdrawal from addictive substances.”
Overactive avoidance learning may also be a pathway that contributes to obsessive-compulsive disorder and other clinical anxiety disorders, suggested Lopez. “We hope to follow up on these basic research findings to address clinical problems affecting patients.”
The post Region Specific Shifts in Dopamine Signaling Plays Role in Learning to Avoid Danger appeared first on GEN - Genetic Engineering and Biotechnology News.